COMPRESSORTo take a definite quantity of air/gas and deliver it at a required pressure.Reciprocating and Rotary types are used.Reciprocating – low mass and high pressure ratioRotary – high mass and low pressure ratio

Positive displacement compressors – depend on a volume change for the compression process. Dynamic compressors – depend on acceleration, deceleration and conversion of velocity into pressure.

The reciprocating compressor is the most widely used positive displacement compressor.

The piston is usually driven by a crankshaft through a connecting rod and wrist pin to compress the gas.

APPLICATIONS OF AIR COMPRESSORS

• Spray painting

• Inflating tire, ball

• Fish pond (aeration)

• Car washing, Floor cleaning

• Gas compression (O2, N2, etc.)

• Pneumatic machine tools

• Drilling bore wells, etc.

RECIPROCATING AIR COMPRESSOR

Major components:

Piston, connecting rod, crank and cylinder arrangement.Spring loaded valves are operated by a small pressure difference. Compressor is driven by an IC engine or an electric motor.

COMPRESSION PROCESSES

1-2’ : Isothermal compression (pV = const.)1-2 : Polytropic compression (pVn = const.)1-2” : Adiabatic compression (pV = const.)

PRESSURE – VOLUME DIAGRAM

Clearance volume: 6% or more of total volumeMass delivered per unit time = Induced mass per unit time. That is, (md–ma) = (mc–mb)

VOLUMETRIC EFFICIENCY (V)Free air delivery:

Volume of air dealt with per unit time by a compressor.

It is the rate of volume flow delivered, measured at the pressure and temperature of the atmosphere.

Clearance in the compressor reduces the induced volume to a value less than that of swept volume.

V =